How Swansea City must wish Paddy Kenny's nine-month drugs ban had not expired week. The Sheffield United goalkeeper has been training in a park with a private coach for the past eight months, but returned to first-team duty to play an instrumental part in a victory that did serious damage to the Swans' play-off hopes; Blackpool's victory at Peterborough saw the Welsh club drop out of the top six for the first time this year.

Kenny's previous appearance was the 1-0 defeat by Burnley in the play-off final at Wembley in May. The 31-year-old was banned from all football after testing positive for ephedrine, a substance found in cough medicine.

With Kenny starring at one end, Richard Cresswell was the Blades' hero at the other, scoring one and forcing visiting goalkeeper Dorus de Vries into an own-goal.

Paulo Sousa, the Swansea manager, said: "Their keeper was outstanding. He was the man of the match and didn't let us through. He made some great saves but we also missed some chances."

Swansea have been in the play-off positions since 8 December but their wobble has come at the wrong time – their fate will be determined on Sunday when they host Doncaster Rovers, and Blackpool, now a point ahead of them in sixth spot, entertain Bristol City.

Sousa said: "We are depending on other teams but we should be proud of ourselves and keep our heads very high."

United failed to fashion a shot on target in the first half but took the lead in the 62nd minute when a sloppy pass out of defence by Ashley Williams was intercepted by Glen Little, who fed substitute Mark Yeates. He played the ball into Cresswell, who turned and fired the ball beyond De Vries for his 13th goal of the season.

It meant Swansea were forced to abandon their patient approach and, in a desperate search for the equaliser, they were caught on the break in the last minute. Little released Cresswell, and his cross-shot from the byline was turned into his own net by De Vries.

The United manager, Kevin Blackwell, said of Kenny, who rejoined training with the squad a month ago: "It looked like he'd never been away. He looked assured, his timing was good and his handling was crisp and clean.

"There was solidity in the defence with Paddy there. Now he can put the sorry saga behind him and move forward."

The Fan's Verdict

Was it a good match? It was a strange game because our attention was on goings-on at Cardiff: the stadium erupted when Cardiff took the lead to go 2-1 – and a few minutes later we scored, which was greeted with as big a cheer. Then, as news came through that Cardiff had scored a third, we scored our second and our end-of-season party began. Who played well/who had a nightmare? It was a hero's return for Paddy Kenny who kept a clean sheet. They credited our second goal to the Swansea keeper, Dorus De Vries, but for me Richard Cresswell scored a well-taken brace to end the season in great form.